Скачать или смотреть ZTW Spider ESC 30Amp issue

Ok, so here is the story...
Back in late June i had ordered 7 (1 spare) ZTW Spider 30Amp ESCs for my hexacopter. They all work brilliantly and are very responsive, no issues.
For reasons (of my own doing) i had to replace two of the ESCs. As i only had one spare i ordered two more. When they arrived, everything about them looks identical to the first lot and i had noted that these new ones had been manufactured only two weeks earlier (i don't recall when the others were manufactured) and i had no reason to think that these had changed.
Once i fitted the replacement ESC and powered it on, i noticed that the startup and even calibration tones are not the same as the others.
After i did the throttle calibration and tested the motor with it, i noticed straight away that it wasn't right. Its very un-responsive compared to the others (possible sync issues?).
So i'm not sure if these newer ESCs have been flashed with maybe a later build of the SimonK firmware (as the Spiders come pre-flashed with SimonK) or that they are still running stock firmware.
Can anyone tell me?
I have emailed ZTW to find out what the story is.